Optimize SP-GiST insertions.

This includes two micro-optimizations to the tight inner loop in descending
the SP-GiST tree: 1. avoid an extra function call to index_getprocinfo when
calling user-defined choose function, and 2. avoid a useless palloc+pfree
when node labels are not used.

src/backend/access/spgist/spgdoinsert.c

@@ -1861,6 +1861,14 @@ spgdoinsert(Relation index, SpGistState *state,
 	int			leafSize;
 	SPPageDesc	current,
 				parent;
+	FmgrInfo   *procinfo = NULL;
+
+	/*
+	 * Look up FmgrInfo of the user-defined choose function once, to save
+	 * cycles in the loop below.
+	 */
+	if (!isnull)
+		procinfo = index_getprocinfo(index, 1, SPGIST_CHOOSE_PROC);
 
 	/*
 	 * Since we don't use index_form_tuple in this AM, we have to make sure
@@ -2007,7 +2015,6 @@ spgdoinsert(Relation index, SpGistState *state,
 			SpGistInnerTuple innerTuple;
 			spgChooseIn in;
 			spgChooseOut out;
-			FmgrInfo   *procinfo;
 
 			/*
 			 * spgAddNode and spgSplitTuple cases will loop back to here to
@@ -2035,7 +2042,6 @@ spgdoinsert(Relation index, SpGistState *state,
 			if (!isnull)
 			{
 				/* use user-defined choose method */
-				procinfo = index_getprocinfo(index, 1, SPGIST_CHOOSE_PROC);
 				FunctionCall2Coll(procinfo,
 								  index->rd_indcollation[0],
 								  PointerGetDatum(&in),

src/backend/access/spgist/spgutils.c

@@ -743,27 +743,32 @@ Datum *
 spgExtractNodeLabels(SpGistState *state, SpGistInnerTuple innerTuple)
 {
 	Datum	   *nodeLabels;
-	int			nullcount = 0;
 	int			i;
 	SpGistNodeTuple node;
 
-	nodeLabels = (Datum *) palloc(sizeof(Datum) * innerTuple->nNodes);
+	/* Either all the labels must be NULL, or none. */
+	node = SGITNODEPTR(innerTuple);
+	if (IndexTupleHasNulls(node))
+	{
 		SGITITERATE(innerTuple, i, node)
 		{
-		if (IndexTupleHasNulls(node))
-			nullcount++;
-		else
-			nodeLabels[i] = SGNTDATUM(node, state);
+			if (!IndexTupleHasNulls(node))
+				elog(ERROR, "some but not all node labels are null in SPGiST inner tuple");
 		}
-	if (nullcount == innerTuple->nNodes)
-	{
 		/* They're all null, so just return NULL */
-		pfree(nodeLabels);
 		return NULL;
 	}
-	if (nullcount != 0)
+	else
+	{
+		nodeLabels = (Datum *) palloc(sizeof(Datum) * innerTuple->nNodes);
+		SGITITERATE(innerTuple, i, node)
+		{
+			if (IndexTupleHasNulls(node))
 				elog(ERROR, "some but not all node labels are null in SPGiST inner tuple");
+			nodeLabels[i] = SGNTDATUM(node, state);
+		}
 		return nodeLabels;
+	}
 }
 
 /*